Magnetic Tunnel Junctions with Ferroelectric Barriers: Prediction of Four Resistance States from First Principles

TLDR

Magnetic tunnel junctions, used in spintronic devices, combine ferromagnetic electrodes with an insulating barrier, and recent proposals of ferroelectric barriers suggest that multiferroic tunnel junctions could provide four‑state resistance through magnetization and polarization control. The study aims to predict four resistance states in SrRuO₃/BaTiO₃/SrRuO₃ multiferroic tunnel junctions using first‑principles calculations. First‑principles calculations show that SrRuO₃/BaTiO₃/SrRuO₃ multiferroic tunnel junctions with asymmetric interfaces exhibit four distinct resistance states, with resistance strongly modulated by reversing the barrier polarization and switching electrode magnetizations, highlighting their potential as multifunctional spintronic devices.

Abstract

Magnetic tunnel junctions (MTJs), composed of two ferromagnetic electrodes separated by a thin insulating barrier layer, are currently used in spintronic devices, such as magnetic sensors and magnetic random access memories. Recently, driven by demonstrations of ferroelectricity at the nanoscale, thin-film ferroelectric barriers were proposed to extend the functionality of MTJs. Due to the sensitivity of conductance to the magnetization alignment of the electrodes (tunnelling magnetoresistance) and the polarization orientation in the ferroelectric barrier (tunnelling electroresistance), these multiferroic tunnel junctions (MFTJs) may serve as four-state resistance devices. Based on first-principles calculations we demonstrate four resistance states in SrRuO3/BaTiO3/SrRuO3 MFTJs with asymmetric interfaces. We find that the resistance of such a MFTJ is significantly changed when the electric polarization of the barrier is reversed and/or when the magnetizations of the electrodes are switched from parallel to antiparallel. These results reveal the exciting prospects of MFTJs for application as multifunctional spintronic devices.